Composite fan blade and method of construction

ABSTRACT

A composite fan blade is fabricated by bonding two complementary preformed outer shell halves defining an airfoil planform of composite material sandwiching a metal spar which spar extends beyond the airfoil planform to form the root of the blade.

United States Patent 1 1 1111 3,799,701 Rothman 1 Mar. 26, 1974 [54] COMPOSITE FAN BLADE AND METHOD 3,327,995 6/1967 Blackhurst et a1 416/229 0F CONSTRUCTION 3,403,844 10/1968 Stoffer 416/230 3,602,608 8/1971 Morley 416/224 [75] Inventor: Edward A. R thman, So th 3,600,103 8/1971 Gray et a1. 416/224 Glastonbury, Conn. 3,628,890 12/1971 Sayre et a1. 416/230 3,632,460 1/1972 Palfre man et al..... 416/230 [731 AS51811: Aircraf' East 3,679,324 7 1972 star a rdter 416/229 Hartford, Conn. FOREIGN PATENTS OR APPLICATIONS [22] 1972 1,186,486 4/1970 Great Britain 416/230 [21] Appl. No.: 229,873

Primary Examiner-Everette A. Powell, Jr. 52 us. c1 416/226, 416/230, 416/241, firm-Mm Fmdland 416/210 51 1111. c1. F01d 5/14 [571 ABSTRACT [58] Field of Search 416/229, 230, 241 A, 210, A composite fan blade is fabricated by bonding two 416/226 complementary preformed outer shell halves defining an airfoil planform of composite material sandwiching [56] References Cited a metal spar which spar extends beyond the airfoil UNITED STATES PATENTS planform to form the root of the blade.

3.294.366 12/1966 Coplin 416/229 13 Claims, 3 Drawing Figures COMPOSITE FAN BLADE AND METHOD OF CONSTRUCTION BACKGROUND OF THE INVENTION This invention relates to an improved composite fan blade and particularly to the construction thereof.

Heretofore, a composite blade such as those made from boron epoxy or boron aluminum tapes have been fabricated by building up the airfoil planform by compressing stacked layers of the tapes either with or without a core or spar. Once the planform had been established the entire unit would be set or cured in a well known manner. In the case of boron composite blades, the blade, essentially would be built up of layers of boron composite material in a solid structure and accordingly, in order to meet the structural integrity and obtain the proper airfoil planform would require a large amount of boron material which is extremely expensive.

I have found that I can obtain a structurally sound blade while reducing the amount of expensive composite material such as boron by preforming the shell into two thin halves, preforming the spar and bonding the two halves to the spar in a separate operation. Additionally, by extending the spar beyond the shell I have found that I can form the retention of the blade integrallytherewith and enhance the load capabilities of the blade.

SUMMARY OF THE INVENTION The prime object of this invention is to provide an improved fan blade made from composite material and characterized by being less expensive than heretofore known composite blades.

A still further object is to provide an improved fan blade as described wherein the shell of the blade is fab ricated from a composite material and bonded to a centrally disposed spar having an integral retention.

A still further object of this invention is the method of construction of a composite fan blade by preforming two separate halves of an airfoil planform of composite material and bondingthe halves to a centrally disposed spar made from either composite or metallic material.

Other features and-advantages willbe apparent from the specification and claims and from the accompanyvention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevated view of a fan blade.

FIG. 2 is an enlarged sectional view taken along the lines 22 of FIG. 1.

FIG. 3 is an enlarged sectional view taken along lines 3-3 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 to 3 the invention shown is a fan to D. F. Gray, C. E. Doughty and F. D. Pinney on Aug. 7 I7, 1971 and assigned to the same assignee, and for further details reference should be made thereto.

Once the two halves are preformed into the desired airfoil planform they are bonded together andto a centrally disposed spar 14 preferably made from titanium but not limited thereto. The bonding may be either done by using a suitable adhesive or by any well known brazing or diffusion bonding techniques.

A metal strip 18 may be disposed along the leading edge to protect the edge against damage and erosion. The trailing edge and tip may be likewise treated.

It is an important aspect ofthis invention that the spar extend beyond the airfoil planform or shell to define a retention portion 20 for securing the blade to the disc or hub (neither being shown) of the rotating assembly.

ling drawings which illustrate an embodiment of the inblade generally illustrated by numeral 10 and is intended for use in a jet engine as a compressor, or fan or prop-fan blades. The outer shell 12 is fabricated from a composite material such as boron epoxy or boran-aluminum in the manner to be described hereinbelow. It is to be understood that although in its preferred embodiment boron composite material is utilized for The two halves of the shell are: designed to use the least amount of boron composite material as is necessary toobtain the stiffness for the particular intended use. It is not necessary that the two halves ,be continuous over the entire mating surface as it is contemplated that the shell may be hollow over some portion thereof, as shown in the FIGS. 2 and 3. t

Since the major load carrying member is the spar which transmits the load directly to the disc or hub rather than having the shellcarry the load as is the case in heretofore known composite blade assemblies, aflesser amount of boron material is needed resulting in a considerable savings in cost.

It should be understood that the invention is not limreinforced composite having an airfoil planform, a,

leading edge, a trailing edge, a tip, and a root section, saidairfoil planform having a camber side and a face side formed from a relatively thin layer of composite material and being bonded together atthe leading and trailing edges and at the tip of the blade, a spar member sandwiched between the camber side and face side and having one end extending beyond the airfoil planform defining said root section, said spar member being the major structural element in the blade for transmitting the load from said planform through said spar to said root section.

2. A blade as claimed in claim 1 wherein the root section forms the retention means for supporting the blade for rotary movement. i

3. A blade as claimed in claim 2 wherein posite material is boron aluminum.

4. A blade as claimed in claim 2 wherein said composite material is boron epoxy.

5. A blade as claimed in claim 2 wherein said spar member is titanium.

said com- 6. A blade as claimed in claim.2 wherein said spar member extends a substantial length relative to the length of the airfoil planform but short of the tip to leave a cavity between the end of the spar and tip of the blade.

7. A blade for a compressor, fan or prop-fan fabricated from a high modulus filamentary reinforced composite material having an airfoil planforrn and a root section, said airfoil planform having a camber side and a face side formed from a relatively thin layer of composite material, each of said sides having top, side and bottom edges, said camber side and face side being bonded together so that all of said sides are in alignment and defining a hollow cavity, a spar member extending in said hollow member filling at least a portion thereof and bonded to the inner wall of said camber side and said face side and having one end projecting is a composite material. 

1. A blade fabricated from a composite material being made from a relatively high modulus filamentary reinforced composite having an airfoil planform, a leading edge, a trailing edge, a tip, and a root section, said airfoil planform having a camber side and a face side formed from a relatively thin layer of composite material and being bonded together at the leading and trailing edges and at the tip of the blade, a spar member sandwiched between the camber side and face side and having one end extending beyond the airfoil planform defining said root section, said spar member being the major structural element in the blade for transmitting the load from said planform through said spar to said root section.
 2. A blade as claimed in claim 1 wherein the root section forms the retention means for supporting the blade for rotary movement.
 3. A blade as claimed in claim 2 wherein said composite material is boron aluminum.
 4. A blade as claimed in claim 2 wherein said composite material is boron epoxy.
 5. A blade as claimed in claim 2 wherein said spar member is titanium.
 6. A blade as claimed in claim 2 wherein said spar member extends a substantial length relative to the length of the airfoil planform but short of the tip to leave a cavity between the end of the spar and tip of the blade.
 7. A blade for a compressor, fan or prop-fan fabricated from a high modulus filamentary reinforced composite material having an airfoil planform and a root section, said airfoil planform having a camber side and a face side formed from a relatively thin layer of composite material, each of said sides having top, side and bottom edges, said camber side and face side being bonded together so that all of said sides are in alignment and defining a hollow cavity, a spar member extending in said hollow member filling at least a portion thereof and bonded to the inner wall of said camber side and said face side and having one end projecting throUgh the bottom edge of said sides for defining said root section.
 8. A blade as claimed in claim 7 wherein said composite material is boron aluminum.
 9. A blade as claimed in claim 7 wherein said spar is a metallic material.
 10. A blade as claimed in claim 7 wherein said bond is an adhesive.
 11. A blade as claimed in claim 7 wherein said bond is a braze.
 12. A blade as claimed in claim 7 wherein said composite material is boron epoxy.
 13. A blade as claimed in claim 7 wherein said spar is a composite material. 